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Relative CO 2 /NH 3 permeabilities of several members of the mammalian Aquaporin family: bAQP0, hAQP1, hAQP2, rAQP3, rAQP4‐M1, rAQP4‐M23, and hAQP8
Author(s) -
MusaAziz Raif,
Geyer R.Ryan,
Boron Walter F.
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1040.5
Subject(s) - aquaporin , aquaporin 1 , extracellular , water transport , xenopus , chemistry , membrane , biology , biophysics , biochemistry , gene , water channel , water flow , mechanical engineering , environmental engineering , engineering , inlet
The mammalian aquaporins (AQPs) have 13 members in two major families, the orthodox AQPs and the aquaglyceroporins, which also transport glycerol and other small solutes. Previously, we showed that human (h) AQP1, rat (r) AQP4‐M23, and rAQP5—abundantly expressed in cells with high rates of gas transport—exhibit selectivity for CO 2 over NH 3 (AQP4‐M23 ≅ AQP5 > AQP1). Here we extend this analysis to: bAQP0, hAQP1 (repeated), hAQP2, rAQP3, rAQP4‐M1, rAQP4‐M23 (repeated), and hAQP8. We expressed the AQPs in Xenopus oocytes and used microelectrodes to record the maximum transient change in surface pH (ΔpH S ) caused by exposure to extracellular CO 2 (an increase) or NH 3 (a decrease). We computed osmotic water permeability (P f ) from rates of cell swelling under hypotonic conditions. Subtracting the respective values for day‐matched, H 2 O‐injected control oocytes yielded channel‐specific values (*). (ΔpH S *) CO2 was significantly different from 0 only for: AQP0, AQP1, and AQP4‐M23. (−ΔpH S *) NH3 was significantly different from 0 only for: AQP1, AQP3, and AQP8. P f * was significantly different from 0 for all tested AQPs. The ratio (ΔpH S *) CO2 /P f * fell in the sequence: hAQP1 > AQP4‐M23 > AQP0 > [AQP2 ≅ AQP3 ≅ AQP4‐M1 ≅ AQP8 = 0]. The ratio (ΔpH S *) CO2 /(−ΔpH S *) NH3 fell in the sequence: [AQP0 ≅ AQP4‐M23 = infinity] > AQP1 > [AQP3 ≅ AQP8 = 0]. Thus, this group of AQPs exhibits a diverse range of selectivities for CO 2 vs NH 3 vs H 2 O.